To increase the recording density of hard disk drives, high accuracy of head positioning is required. But disk flutter, which is airflow induced vibration, is a major contributor to head positioning error. For detecting disk flutter, we proposed a suspension to which a PVDF film sensor was attached, and built the suspension into an actual HDD. Comparing the power spectrum of disk vertical vibration with that of the PVDF film sensor output, disk flutter was well detected. We also implemented a feedforward controller and confirmed that the influence of disk flutter on position error signal is considerably suppressed.

One of the major contributors to head positioning errors is carriage vibration in low frequency due to an air flow caused by disk rotation. It is necessary to suppress the disturbance for Hard Disk Drives (HDDs) to have more capacity. We experimentally studied a reduction in the flow-induced carriage vibration using linear protrusion structures by putting wires on carriage arms. This study was carried out using 2.5 inch HDD which has high rotational speed of 10,000 rpm. We measured position error signals (PES) and compared with a conventional carriage. From the experimental results, we found that the linear protrusion structure was effective to reduce the carriage vibration. Leading edge wire configuration and 2 linear protrusion configuration improved average nonrepeatable position errors (NRPE) by 6.9% and 6.4%, respectively.

No abstract